Sandy Stier, left, and Kris Perry of Berkeley, Calif., stand outside the National Archives in Washington, Monday, March 25, 2013, before going inside to view the U.S. Constitution, a day before their same-sex marriage case is argued before the Supreme Court. (AP Photo/Jose Luis Magana)— AP

Sandy Stier, left, and Kris Perry of Berkeley, Calif., stand outside the National Archives in Washington, Monday, March 25, 2013, before going inside to view the U.S. Constitution, a day before their same-sex marriage case is argued before the Supreme Court. (AP Photo/Jose Luis Magana)
/ AP

A demonstrator holds a bible while marching outside the Supreme Court in Washington, Tuesday, March 26, 2013, as the court heard arguments on California's voter approved ban on same-sex marriage, Proposition 8. The Supreme Court waded into the fight over same-sex marriage Tuesday, at a time when public opinion is shifting rapidly in favor of permitting gay and lesbian couples to wed, but 40 states don't allow it. (AP Photo/Pablo Martinez Monsivais)— AP

A demonstrator holds a bible while marching outside the Supreme Court in Washington, Tuesday, March 26, 2013, as the court heard arguments on California's voter approved ban on same-sex marriage, Proposition 8. The Supreme Court waded into the fight over same-sex marriage Tuesday, at a time when public opinion is shifting rapidly in favor of permitting gay and lesbian couples to wed, but 40 states don't allow it. (AP Photo/Pablo Martinez Monsivais)
/ AP

From left, plaintiffs Sandy Stier, with her partner Kris Perry, and their twin sons Spencer Perry and Elliott Perry, all from Berkeley, Calif., meet with reporters outside the Supreme Court in Washington, Tuesday, March 26, 2013, after the court heard arguments on California's voter approved ban on same-sex marriage, Proposition 8. The Supreme Court waded into the fight over same-sex marriage Tuesday, at a time when public opinion is shifting rapidly in favor of permitting gay and lesbian couple— AP

From left, plaintiffs Sandy Stier, with her partner Kris Perry, and their twin sons Spencer Perry and Elliott Perry, all from Berkeley, Calif., meet with reporters outside the Supreme Court in Washington, Tuesday, March 26, 2013, after the court heard arguments on California's voter approved ban on same-sex marriage, Proposition 8. The Supreme Court waded into the fight over same-sex marriage Tuesday, at a time when public opinion is shifting rapidly in favor of permitting gay and lesbian couple
/ AP

WASHINGTON 
The Supreme Court dove into a historic debate on gay rights Tuesday that could soon lead to resumption of same-sex marriage in California, but the justices signaled they may not be ready for a major national ruling on whether America's gays and lesbians have a right to marry.

The court's first major examination of gay rights in 10 years continues Wednesday, when the justices will consider the federal law that prevents legally married gay couples from receiving a range of benefits afforded straight married people.

The issue before the court on Tuesday was more fundamental: Does the Constitution require that people be allowed to marry whom they choose, regardless of either partner's gender? The fact that the question was in front of the Supreme Court at all was startling, given that no state recognized same-sex unions before 2003 and 40 states still don't allow them.

There is no questioning the emotions the issue stirs. Demonstrators on both sides crowded the grounds outside the court, waving signs, sometimes chanting their feelings.

Inside, a skeptical Justice Samuel Alito cautioned against a broad ruling in favor of gay marriage precisely because the issue is so new.

"You want us to step in and render a decision based on an assessment of the effects of this institution which is newer than cellphones or the Internet? I mean, we do not have the ability to see the future," Alito said.

Indeed, it was clear from the start of the 80-minute argument in a packed courtroom, that the justices, including some liberals who seemed open to gay marriage, had doubts about whether they should even be hearing the challenge to California's Proposition 8, the state's voter-approved gay marriage ban.

Justice Anthony Kennedy, the potentially decisive vote on a closely divided court, suggested the justices could dismiss the case with no ruling at all.

Such an outcome would almost certainly allow gay marriages to resume in California but would have no impact elsewhere.

There was no majority apparent for any particular outcome, and many doubts were expressed by justices about the arguments advanced by lawyers for the opponents of gay marriage in California, by the supporters and by the Obama administration, which is in favor of same-sex marriage rights. The administration's entry into the case followed President Barack Obama's declaration of support for gay marriage.

On the one hand, Kennedy acknowledged the recentness of same-sex unions, a point stressed repeatedly by Charles Cooper, the lawyer for the defenders of Proposition 8. Cooper said the court should uphold the ban as a valid expression of the people's will and let the vigorous political debate over gay marriage continue.

But Kennedy pressed him also to address the interests of the estimated 40,000 children in California who have same-sex parents.

"They want their parents to have full recognition and full status. The voice of those children is important in this case, don't you think?" Kennedy said.

Yet when Theodore Olson, the lawyer for two same-sex couples, urged the court to support such marriage rights everywhere, Kennedy feared such a ruling would push the court into "uncharted waters." Olson said that the court similarly ventured into the unknown in 1967 when it struck down bans on interracial marriage in 16 states.